• Voltage: the charge (electron) “pusher.” Voltage
causes current to flow/move.
• Voltage sources:
• Battery
• Generator
• Outlets
• Symbol for voltage = V
• Unit for voltage = Volts (V)
• Italian physicist
• known especially for the
invention of the
electrochemical cell, aka
the battery in 1800.
• Power utilities use large generators to provide the
120V that is delivered to your home outlets.
• When you plug in something to the outlet (lamp,
blow dryer, TV, etc) the voltage is applied across
the circuit, allowing the charge to flow (electric
current).
• Current: flow of charge (electrons) within a
conductor or how fast charge is moving.
• Charge will only flow if there is a voltage source
(potential difference).
• Symbol for Current = I
• Unit for Current = Amps (A)
• French physicist and
mathematician.
• One of the main discoverers
of electromagnetism.
• SI unit of measurement of
electric current, the ampere,
is named after him.
Current in Amps
Effect on A Person
0.001 Amps
Can be felt
0.005 Amps
Painful
0.010 Amps
Involuntary muscle
spasms
Loss of muscle control
0.015 Amps
0.070 Amps
If through heart, serious
injury, likely fatal if it lasts
more than 1 second
• Resistance: opposes the push from the voltage source.
Resistance affects the speed of the current.
• Symbol for Resistance = R
• Unit for Resistance = Ohms (Ώ)
• German physicist
• Ohm determined that there is a
direct proportionality between
the voltage applied across a
conductor and the electric
current.
• This relationship is known as
Ohm's law.
• If the voltage in a circuit increases, the current
will increase.
• If the voltage in a circuit decreases, the current
will decrease.
• This is a direct/proportional relationship.
• If the resistance in a circuit increases, the
current will decrease.
• If the resistance in a circuit decreases, the
current will increase.
• This is an inversely proportional
relationship.
• State the relationship between current,
voltage, and resistance.
• German physicist George Ohm had the law
named after him, because of his extensive
research.
Voltage is equal to the current multiplied by
the resistance.
Voltage,
measured in
Volts, V
Current, measured
in Amps, A
V=IR
Resistance,
measured in
Ohms, Ω
• If you want to find Voltage in Volts:
V = IR
If I= 2 A and R = 5 Ohms
Then, V= (2A)(5Ω) = 10 V
• If you want to find Resistance in
Ohm’s:
R=V/I
If V = 9 Volts and I = 4 A
Then R = 9 V/ 4A = 2.25 Ω
• If you want to find Current in Amps:
I=V/R
If V= 140 V and R = 2Ω
Then, I = 140V/ 2Ω = 70 A